MCR XI. Microreactors as Processors for Chemical Computers

Computer chemistry as well as the newer research in computational chemistry try to predict or estimate reaction pathways. To date this kind of syntheses planning has not succeeded, nor did approaches using rule-based heuristics like so-called expert systems. The reason for this is that reacting compounds are a highly parallel system. Molecules of the same chemical compound will react in different ways and/or at a different moment. Too many parameters are responsible for how chemical reactions proceed. Computers can not follow chemical reactions. Up to now, the only way to handle chemical problems is to use the chemistry itself. Usually synthetic chemists are interested in the main product exclusively. Naturally they do not care too much about side reactions and other strange things going on in their reaction vessels. But this complexity of chemical reactions can be useful for solving problems for which computers are far too slow.Chemical reactions may be considered as mathematical functions. They have parameters like starting compounds, temperature, concentration or time. In a mixture of one mole of each of the reacting compounds you will find one mole functions.There is a class of problems in computer science that is called NP-complete. For problems belonging to this class no algorithms exist to solve the problem within acceptable time. A solution is to involve a highly parallel system of problem solv-ing functions like the syntheses of libraries of multicomponent reactions. It seems that the best way to calculate or simulate chemistry is chemistry itself, and instead of using computers to solve chemical problems, chemistry may solve problems of computer science.In order to make such a project possible, well-controlled chemical systems are necessary. Such apparatus covers one or more microreaction units, automatic detection units and a feedback unit for the syntheses control. An example for optimization using a chemical genetic algorithm will be presented. This involves a variable set of microreactors running parallel and a compound detection unit.